Digoxin toxicity



Pathophysiology

Digoxin

  • Inotropic = NA+/K+ ATPase pump causing ↑ in intracellular Ca++, Na+ and ↓ in intracellular K+
  • Chronotropic = Slows conduction in AV node (but increased spontaneous firing by Purkinje tissues)
  • Toxic effect mainly ATPase pump effects

History

  • Fatigue
  • Palpitations, DOE rare
  • Pre-syncope or light headed
  • Confusion
  • Changes in colour vision
  • Diplopia or blurred vision
  • Nausea, anorexia, diarrhoea

Examination

  • Poor perfusion, CCF
  • Dysrhythmia
  • PVCs usually benign
  • PAF with 2:1 block
  • Junctional rhythm
  • Torsade de pointes
  • Sinus or AF bradycardias

Classically see tachy/brady with VT ± bradycardia unresponsive to atropine


Treatment

  • Stop digoxin!
  • Treat arrhythmias
  • Correct electrolyte imbalance
  • Beware drugs that raise plasma digoxin levels
    • Amiodarone, Ca++ channel blockers, quinine
  • DigiFab®: digoxin specific antigen binding fragment for life threatening dig toxicity
    • t1/2 16 hours (with normal renal fxn)
    • Beware that serum dig levels are unreliable after DigiFab®. Repeated doses should be given only on clinical ground, not on repeat dig levels (which may appear higher that before DigiFab is given.

More on DigiFab dosing / administration.


Content by Dr. Íomhar O' Sullivan 04/09/09. Last updated ÍOS 5/05/15.